The actress walked the red carpet at Save The Children's star-studded "Centennial Celebration" gala at the The Beverly Hilton Hotel on Wednesday, and she opened up to ET's Denny Directo about how her three kids aren't as easy to convince when it comes to donning family costumes for the holiday.
"It definitely gets harder," said Garner -- who is the mother of two daughters, 13-year-old Violet and 10-year-old Seraphina, and 7-year-old son, whom she shares with her ex-husband, Ben Affleck.
"I mean, I remember one year when I talked both my girls into dressing up as pigs, and they were so cute!" Garner recalled. "And now they would be like, 'No, mom, ohmygosh, no!'"
"So yeah, it's harder. But they're gonna be cute, whatever they are," she added.
The 47-year-old Golden Globe winner couldn't help but gush over her children and share how they've changed her life.
"I have kids that are funny and smart, and I think they're awesome," she shared. "They change you wholly, and completely and not at all. I'm lucky to have them."
Meanwhile, the Save the Children Fund must count itself lucky to have the tireless support of a generous star like Garner, who is a trustee for the humanitarian organization, one of its ambassadors, and has been an outspoken champion for years.
"When you are lucky enough to get to see a problem up close, and for me that is poverty in rural America…, and then you see a solution? And you see hope and optimism? There is nothing that is more of a driver than that," Garner said, addressing what motivates her to spend so much of her time and energy advocating for the charitable cause.